I replaced my old inlet manifold today with a new one i sourced for a £10er and i could not beleive the state of the seals between the head and manifold, due to the breather pipe on air intake blowing in fumes and vapour / oil the seals were hardening and being compressed due to contact with heat and oil, now the tops of the seals were fine but the bottom of the seals were rock solid, and i could see where oil had been seeping out of the manifold down the side of the head
this below photo was after i cleaned up the surfaces for the new manifold
as a result i now have a higher Map pressure when revving and the map pressure doesn't drop below 15 when taking your foot off the gas where as before it was